Almost all the gems have some kind of medicinal properties. But the jewels that belong to Navratna category are famous for their medicinal properties as well besides their divine virtues.

Treatment of a particular disease with the help of a gemstone is known as Gemopathy. It is very wide subject. Following is a brief description of the medicinal values of the jewels that belong to the Navratna category.

With the development of science, gemstones have been subjected to detailed scientific scrutiny and their chemical composition has been revealed. Following is a brief discussion of chemical composition of the jewels that belong to Navratna category.

1) Ruby: This is the stone of the sun and hence has a supreme position among the Navrartnas. The sun is the centre of the solar system. Ruby is an extremely expensive and rare stone. It has a hardness of 9 and a refractive index of 1.716 to 1.77 and a specific density of 4.03. Aluminum oxide (AlO) is the main constituent of ruby. Pink colour of the ruby is due to the presence of chromium oxide (CrO).

Ruby is next to diamond only in hardness. Sometimes it surpasses even diamond in beauty and value. All types of rubies appear similar superficially but a deep scrutiny reveals many distinct differences among them. These are as follows-

Pearl: This gem of the moon is at the second position among Navratnas. It is both natural as well as cultured. Both kinds of pearls impart mental peace in the wearer. Pearl is basically not a stone. It has organic origin and develops inside the sea-shells.

Cultured pearls are produced by artificially inseminating the shells. This method has been perfected in Japan. Chemically, pearl has calcium carbonate and an organic compound named conchiolin. It has a hardness of 3.5 to 4.0 and a specific density of 2.50 to 2.75. It is opaque and cannot be burnt. Excellent pearls come from the Persian gulf. Following are the kinds of pearl-

Coral: Like pearl, Coral also is not a true stone. In fact it is fossilized from a tiny sea creature known as corals. Coral is worn to please the Mars. Heat and light of the sun play a major role in the formation of coral. Its specific density is 2.65; refractive index 1.486 to 1.66 and hardness is 4.0. Coral reacts with hydrochloric acid to form froth. When touched by a hot wire coral smells like burning hair. Coral has following types-

1) Brahmin coral.2) Kshatriya coral.3) Vaishya coral.4) Shudra coral.

Emerald: This green coloured stone is also a prominent jewel among the Navratnas. It is worn to please Mercury. It has a specific density of about 3.0; hardness 8.0 and refractive index of 1.6. Emerald is usually transparent in appearance and is composed of aluminium and berilium silicate. Some people incorrectly call it as aquamarine. Often emerald is more expensive than diamond. As per the appearance, colour, clarity and radiance, emerald has following types-

Yellow Sapphire (Topaz): This yellow coloured transparent jewel is the main stone of Jupiter. It is extremely expensive, rare and enchanting gem. Some experts regard yellow sapphire as a crystalline mineral. Chemically it is aluminum fluorosilicate. It has the hardness of 8; refractive index 1.63 and specific density of 3.5 to 3.6.

Diamond: It is regarded as the 'king of the gems'. This white coloured transparent and radiant stone is worn to please Venus. Chemically, diamond is a crystalline isotrophe of carbon and with a hardness of 10, it is the hardest known substance on earth. It has a specific density of 3.15 to 3.55 and a refractive index of 2.5. Diamond has following types as per the colour-

Brahmin diamond.Kshatriya diamond.Vaishya diamond.Shudra diamond.

Apart from these, on the basis of clarity, diamond has following types-

There are many evidences in the history that show the profound creative as well as destructive qualities of the diamond. Many diamonds like Kohinoor, Calinen, King Orloff are very famous in human history.

Blue Sapphire: It is the most talked about gem that belongs to Navratna category. This beautiful attractive and transparent gem is the main stone of Saturn and has tremendous powers. Basically, sapphire, topaz and ruby belong to same class of stones. A slight variation in colour differentiates them from one another. Aluminum oxide is the main constituent of blue sapphire. In hardness, specific density and refractive index sapphire is similar to topaz and ruby.

Agate (Hassonite): This stone also belongs to Navratna category and is available in black, light brown and amber colours.

Cat's eye: This opaque but miraculous stone also belongs to Navratna category. It is available in many colours like white, sky blue, black and green. Green cat's eye is the most expensive. It is worn to please Ketu.